Seems pointless adding any more suggestions, but I’m going to do it anyway and suggest a visit to Port Appin/Castle Stalker.
My parents live just down the road but every time I visit Port Appin I’m struck by just how tranquil and beautiful it is. There’s also a restaurant on top of the hill overlooking Castle Stalker and Ardnamurchan, has to be one of the best views in the Highlands on a good day.
Edit: actually since Glenelg is already on your radar and your friends are keen on hiking, I couldn’t recommend Beinn Sgritheall strongly enough, amazing views from top, feels like 1000m straight down to the sea!